As a continuous ongoing project, the molecular regulatory mechanism of P450IIE was further investigated. We have previously identified and determined the structures of the ethanol-inducible cytochrome P450 (P450IIEI) of both rat and human. We have also demonstrated three distinct types of regulation of P450IIE1 in rat. The three types of up-regulation of P450IIE appeared to be present in liver, lung, and kidney tissues. The mechanism of a negative effect of CCl4 on P450IIE was further examined. The administration of CCl4 not only reduced the level of P450IIE associated enzyme activity and the amount of immunoreactive P450llE, but also caused rapid decline in its mRNA indicating a pretranslational reduction of P450IIE by its own substrate. In contrast, other major classes of P450 did not appear to be affected by CCl4, indicating a specific reduction of P450IIE. In a collaboratory project with Dr. Casazza, a pretranslational reduction of P450IIE during pregnancy was also observed indicating a negative hormonal control mechanism in P450IIE regulation. The two specific down-regulations of P450IIE by CCl4 and hormones during pregnancy along with three types of up-regulatory mechanism of P450IIE thus provide an unique example of multiple modes of regulation among the classes of P450, most of which are activated by transcriptional activation. A method for the measurement of P450IIE1 in easily obtainable human tissues was also established. By immunoblot analysis, P450IIE1 expressed in cultured lymphocytes could be easily detected by specific antibody to P450IIE1. The levels of P450IIE in lymphocytes from poorly controlled diabetic children are elevated four to ten fold over those of the corresponding control subjects. The induced levels of P450IIEI determined by the density of immunoreactive bands highly correlated with those of hemoglobin Alc with a correlationship coefficient of 0.87. The levels of P450IIE in lymphocytes from alcoholic patients at admission and discharge were determined by the immunoblot analyses: the levels of P450IIE in alcoholics were four to five folds higher than those found in the voluntary control group.